criu/pie/parasite-vdso: Handle also systems without VVAR

On s390 we don't use vvar. Therefore vvar_size in not been initialized
and the value remains VVAR_BAD_SIZE.

Fix the BUG() statement to also cover this case.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/pie/parasite-vdso.c

@@ -44,9 +44,11 @@ static int vdso_remap(char *who, unsigned long from, unsigned long to, size_t si
 /* Park runtime vDSO in some safe place where it can be accessible from restorer */
 int vdso_do_park(struct vdso_maps *rt, unsigned long park_at, unsigned long park_size)
 {
+	unsigned long vvar_size;
 	int ret;
 
-	BUG_ON((rt->sym.vdso_size + rt->sym.vvar_size) < park_size);
+	vvar_size = (rt->sym.vvar_size == VVAR_BAD_SIZE) ? 0 : rt->sym.vvar_size;
+	BUG_ON((rt->sym.vdso_size + vvar_size) < park_size);
 
 	if (rt->vvar_start != VVAR_BAD_ADDR) {
 		if (rt->sym.vdso_before_vvar) {